to introduce or cause to be introduced into the body of something: to insert an extra paragraph in an article.
—n.
something inserted or to be inserted.
an extra leaf or section, printed independently, for binding or tipping into a book or periodical, esp. a leaf or section consisting of an illustration or advertisement printed on different paper.
any small picture, device, etc., surrounded partly or completely by body type.
a paper, circular, etc., placed within the folds of a newspaper or the leaves of a book, periodical, etc.